package com.example.j2eeapp.dao;

import javax.persistence.NoResultException;
import javax.persistence.Query;

import org.springframework.util.Assert;

import com.example.j2eeapp.commons.dao.GenericJpaDao;
import com.example.j2eeapp.domain.UserEntity;

/**
 * Data Access Object JPA implementation to work with User entity database
 * operations.
 * 
 * @author Asapin
 */
public class UserJpaDao extends GenericJpaDao<UserEntity, Long> implements
		UserDao {

	public UserJpaDao() {
		super(UserEntity.class);
	}

	/**
	 * Queries database for user name availability
	 * 
	 * @param userName
	 * @return true if available
	 */
	public boolean checkAvailable(String userName) {
		Assert.notNull(userName);

		Query query = getEntityManager().createQuery(
				"select count(*) from " + getPersistentClass().getSimpleName()
						+ " u where u.userName = :userName").setParameter(
				"userName", userName);

		Long count = (Long) query.getSingleResult();

		return count < 1;
	}

	/**
	 * Queries user by username
	 * 
	 * @param userName
	 * @return User entity
	 */
	public UserEntity loadUserByUserName(String userName) {
		Assert.notNull(userName);

		UserEntity user = null;

		Query query = getEntityManager().createQuery(
				"select u from " + getPersistentClass().getSimpleName()
						+ " u where u.userName = :userName").setParameter(
				"userName", userName);

		try {
			user = (UserEntity) query.getSingleResult();
		} catch (NoResultException e) {
			// do nothing
		}

		return user;
	}

}
